1. Field of the Invention
The present invention relates to compositions for use as thickening or viscosifying agents in aqueous systems and, more particularly, the aqueous well servicing fluid prepared therefrom.
2. Description of the Background
It is known from U.S. Pat. Nos. 4,330,414 and 4,435,564 that compositions containing HEC can be used to thicken aqueous substances such as heavy brines commonly employed as well servicing fluids, if the HEC is formulated in certain ways. Thus, for example, in U.S. Pat. No. 4,330,414, it is taught that a mixture of HEC, a solvating agent, which is an agent that pre-hydrates the HEC, and a diluent which is a non-solvating agent for the HEC will effectively viscosify heavy brines, i.e. brines having a density greater than about 11.7 pounds per gallon (ppg) and more generally from about 12.0 ppg to about 19.2 ppg. U.S. Pat. No. 4,435,564 teaches that a composition containing HEC, certain amino compounds and an organic liquid which does not pre-hydrate the HEC is useful in viscosifying heavy brines at ambient temperatures.